linux-ext4 - [PATCH v3 02/10] mm: add device coherent vma selection for memory migration

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Message-ID: <20220110223201.31024-3-alex.sierra@amd.com>
Date:   Mon, 10 Jan 2022 16:31:53 -0600
From:   Alex Sierra <alex.sierra@....com>
To:     <akpm@...ux-foundation.org>, <Felix.Kuehling@....com>,
        <linux-mm@...ck.org>, <rcampbell@...dia.com>,
        <linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>
CC:     <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
        <hch@....de>, <jgg@...dia.com>, <jglisse@...hat.com>,
        <apopple@...dia.com>, <willy@...radead.org>
Subject: [PATCH v3 02/10] mm: add device coherent vma selection for memory migration

This case is used to migrate pages from device memory, back to system
memory. Device coherent type memory is cache coherent from device and CPU
point of view.

Signed-off-by: Alex Sierra <alex.sierra@....com>
---
v2:
condition added when migrations from device coherent pages.
---
 include/linux/migrate.h | 1 +
 mm/migrate.c            | 9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index c8077e936691..e74bb0978f6f 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -138,6 +138,7 @@ static inline unsigned long migrate_pfn(unsigned long pfn)
 enum migrate_vma_direction {
 	MIGRATE_VMA_SELECT_SYSTEM = 1 << 0,
 	MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1,
+	MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2,
 };
 
 struct migrate_vma {
diff --git a/mm/migrate.c b/mm/migrate.c
index 91018880dc7f..0367f471211a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2340,8 +2340,6 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			if (is_writable_device_private_entry(entry))
 				mpfn |= MIGRATE_PFN_WRITE;
 		} else {
-			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
-				goto next;
 			pfn = pte_pfn(pte);
 			if (is_zero_pfn(pfn)) {
 				mpfn = MIGRATE_PFN_MIGRATE;
@@ -2349,6 +2347,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				goto next;
 			}
 			page = vm_normal_page(migrate->vma, addr, pte);
+			if (page && !is_zone_device_page(page) &&
+			    !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
+				goto next;
+			if (page && is_device_coherent_page(page) &&
+			    (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
+			     page->pgmap->owner != migrate->pgmap_owner))
+				goto next;
 			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
 			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
 		}
-- 
2.32.0